Estimation of the primary stability of the press-fit and screwed-in acetabular components after hip joint arthroplasty

Abstract

Arthroplasty is one of the most common and effective treat­ments for degenerative diseases and injuries of the hip joint, but marked increase in the number of revision procedures asso­ciated with instability of the implant, including cups, and a pair of friction problems.

Objective: using biomechanical methods to evaluate the primary acetabular stability with screwing up and press-fit components.

Methods: to evaluate the stress-strain state and subchondral spongy tissues in the acetabular zone under load of 1000 H, developed a simplified design scheme of the hip joint and healthy model of «bone – cup – insert – head» implant using finite element method. Press-fit and that screwing up cups were studied.

Results: in healthy hip joint any stress concentrators are absent. Maximum values are 0.09 MPa stress-strain state on the strength of spongy bone tissue 12.17 MPa. The most strenous share of subchondral bone is part of the roof — 16.24 MPa for her strength of 150–200 MPa. If using press-fit cups revealed increasing tension of spongy tissue in 4 ÷ 5 times, and at the entrance to the subchondral acetabular zone — 2 ÷ 3 times. With the use of screw up cups t transferring the load on the pelvic bone closest to the healthy joint. Small lo­cal stress concentrators in the spongy tissue occur in the contact zone of the threaded subchondral and spongy tissue and at a dis­tance of 1mm their value is reduced by 2–3 times and does not exceed 0.3 MPa.

Conclusions: the use of screw up cup has ad­vantages, especially in osteoporosis, because after implantation load on the pelvic bone close to the stress-strain state of healthy hip joint.